import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StreamTokenizer;
import java.util.Scanner;
//知识点:二叉树，中序遍历，数组
public class P4913 {
    static int ans = 0;
    static Node tree[];

    public static void main(String args[]) throws IOException {
        StreamTokenizer st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        st.nextToken();
        int n = (int)st.nval;
        tree = new Node[n+1];
        for(int i=1; i<=n; i++){
            st.nextToken();
            tree[i] = new Node();
            tree[i].left = (int)st.nval;
            st.nextToken();
            tree[i].right = (int)st.nval;
        }
        dfs(1,1);
        System.out.println(ans);

    }
    static void dfs(int node,int depth){
        if(node == 0){
            return;
        }
        ans = Math.max(depth, ans);
        dfs(tree[node].left, depth+1);
        dfs(tree[node].right, depth+1);
        return;
    }
    static class Node{
        int left;
        int right;
    }
}